In early June I was walking in a park in southern Ontario hoping to hear a certain warbler singing. That meant I spent a long time pacing up and down a short stretch of path admiring all the insects, reptiles and birds to be seen while I listened. My reward was not the emergence of the wanted warbler but instead a first-hand look at a truly intriguing encounter between a Swallowtail and a Robin.
Tiger Swallowtail butterflies are common in June. They are primarily interested in finding partners and/or laying eggs but they do sometimes stop to sip from flowers, sap, waste or puddles. So I kept an eye on a butterfly when it floated low over the still-wet-from-last-night’s-rain path.
To my astonishment, the Tiger Swallowtail began to try to drive an American Robin away from a particular part of the path!
Swallowtail Butterfly Attacks Robin to Try to Drive It Away
The Robin, which had been moving up and down the path hunting had paused beside what turned out to be a clump of wet, dead, slightly rotten vegetation. As it turned out later, the butterfly wanted to land on that sodden lump.
Not just once, or twice, but repeatedly, the Swallowtail dove at the Robin. It came within a few cm (inches) several times. The butterfly would circle past the bird and come back again very quickly. I actually watched the Robin flinch, twice, when the Tiger came very close.
After more than 2 minutes of these aerial attacks, the Robin eventually moved a few steps away, although I’m not convinced that it even knew what the Swallowtail wanted.
Very soon after it departed, the Tiger Swallowtail settled onto the wet clump of leaves and sipped delicately. It stayed there for four minutes “drinking.” I paced, slowly and carefully, around it taking photos and it did not budge.
Eventually, the butterfly moved up onto a leaf on a nearby shrub and basked. A few minutes later it left.
Why Didn’t the Robin Move Sooner?
I’m not certain but it seemed like the Robin was interested in catching other insects near and in the sodden leaves.
Do Butterflies Often Mob Birds?
It took a bit of searching but I have found other reports of mobbing behaviour from butterflies. There seem to be three common types:
Some Butterflies Will Defend Their Territories from Other Butterflies and Other Creatures
Red Admirals are known to be territorial in some situations. I had one come after me the other morning: It flew straight at me, then swerved and fluttered briefly around my camera lens. I’m still not sure if it was bothered by me or if it saw a reflection in my lens and thought it was chasing another butterfly.
Others report attacks by Red Admirals as well. James C. Trager, in the comments on the Prairie Ecologist website, says he has seen Hackberry Butterflies chasing anything large that flies into their territory.
Some Butterflies Will Defend Their Food Source
This is what I think the Swallowtail I watched was doing. It wanted to land on the wet dead leave mass and ingest the wet juices possibly to get minerals. The Robin was in its way so it drove it off and then very quickly landed and stayed perched even when I came quite close to take photos.
Other people report seeing this type of behaviour to defend flowers, sap and mud puddling sipping spots.
For example, the Prairie Ecologist, Chris Helzer, wrote on his website about Gray Copper Butterflies driving Regal Fritillaries away from milkweed flowers.
Some Butterflies Will Attack Other Butterflies
On the Prairie Ecologist’s website, in the comments, several readers reported that they had witnessed Fritillaries attacking Monarchs. They had even seen the Fritillaries landing on Monarchs as they emerged from their chrysalises. This damaged some of the Monarchs that had not yet pumped up their wings and hardened their bodies.
And Yes, Other People Have Seen Butterflies Chasing Birds
Tom H., in the comments on the Prairie Ecologist website, reports having seen a Common Banded Skipper chasing a Hummingbird away.
Steven M,. also in the comments, had seen a Monarch go after birds.
Marie Winn reports on her Central Park Nature News website that Ben Cacace watched a Swallowtail drive a pair of mallards into the water. The butterfly apparently actually struck the Mallard more than once on the head.
On BirdForum, a chat site for bird watchers, one person reported seeing Purple Emperors chasing birds, and another reported seeing a butterfly chasing a swallow.
In the comments on a Flickr photo of a Lorquin’s Admiral Butterfly, a reader confirms that they will attack birds. The Canadian Biodiversity Information Facility website posting for this Admiral also states this “This is a very pugnacious butterfly, often attacking any intruder in its territory, even large birds.” It cites a reference from 1981.
So I’m not the first person to see this curious behaviour. I found it quite interesting to watch and at times amusing, too. I hope I’ll see a repeat engagement on another spring morning.
- Butterflies of June
- Sexing Monarchs (Butterflies, that is!)
- A Small Black and Blue “Monarch” is Actually an Admiral
- Butterflies Abound on Bergamot Blossoms
Have you seen butterflies chasing away birds, other butterflies, or other creatures? Please share your experience with a comment.